Research on Modeling and Simulation of
Detailed Model of Photovoltaic Power
Generation System Yuyu Liu1,2,a,*, Xueshun Ye2, Keyan Liu2, Hairong Luo3
1North China University of Water Resources and Electric Power, Jinshui District, Zhengzhou City, Henan Province, China.
2China Electric Power Research Institute, Haidian District, Beijing Municipality, China 3Electric Power Research Institute of State Grid NingXia Electric Power Company,Jinfeng District,
Yinchuan City, NingXia Autonomous Region, China. a email: [email protected]
Keywords: Photovoltaic array, MPPT, Photovoltaic Inverter Control Strategy, Digital ana-log Hybrid Simulation Management System
Abstract: With the photovoltaic, fan and other new energy in the proportion of distribution network is growing, the photovoltaic power generation system and the process of accurate simulation is of great significance. Based on Matlab / Simulink, a detailed model of PV ar-ray, detailed model of MPPT controller and detailed model of PV inverter control strategy are established according to the actual principle of grid connection, and the process of grid connection of photovoltaic power generation system is simulated. The photovoltaic grid connected waveforms of the mixed-mode simulation system of distribution network of China Electric Power Research Institute are compared with Simulink model simulation waveforms, and the accuracy of the model is verified. The experimental results show that the detailed simulation model of photovoltaic power generation system can accurately re-flect the grid connection process of photovoltaic power generation system.
1. Introduction
In recent years, with the traditional energy shortage and environmental problems become increasingly serious, and the rapid development of clean energy and distributed power generation technology, photovoltaic, fan and other new energy distributed power generation technology in the proportion of distribution network increased dramatically. Among them, the photovoltaic power generation system because of its flexible application, convenient and so on, in the distribution network has a very good application prospects. The modeling and simulation of the grid-connected process of the photovoltaic power generation system has a guiding effect on the actual photovoltaic power generation system. Therefore, it is very important to establish a realistic simulation model of PV power generation system for the development of PV power generation system.
The 3rd International Conference on Intelligent Energy and Power Systems (IEPS 2017)
Published by CSP © 2017 the Authors 172
Researchers at home and abroad have carried out some research on the modeling and simulation of photovoltaic power generation system. The photovoltaic power generation model is reviewed in [1]. Literature [2] ~ [5] carried out preliminary modeling work on PV array and MPPT. In the literature [6], the characteristics of PV arrays under different conditions were analyzed. The control strategies of the inverter are discussed in [7] ~ [10]. Among them, the control strategy of PQ, V / f and Droop is the focus of these four literatures.
2. Mathematical Model of Photovoltaic System and Simulink Model
As shown in Figure 1, the solar photovoltaic array of photovoltaic power generation system of light into DC power, the boost circuit MPPT controller, and then through the DC / AC inverter con-trol strategy into alternating current through the filter and isolation transformer into the power grid.
SPWMControl Strategy
FilterPV
inverter
MPPT controller
Boost
Photovoltaic array
Distribution network
~Isolation
transformer
Figure 1 PV power generation structure.
The detailed Matlab / Simulink model of each part of the grid-connected model of the photovoltaic power generation system will be established in order to carry out the next step-by-step process simulation study.
2.1. Photovoltaic array mathematical model and Simulink model
2.1.1. Mathematical model of photovoltaic array
Based on the theory of electronics, photovoltaic panels are affected by light to produce photovoltaic effects, solar energy into electrical energy. The equivalent circuit diagram of the PV array is shown in the following figure:
UC
Id
Rsh
RsIph
Solar energy
Figure 2 Photovoltaic array equivalent circuit.
In Figure 2, is the current generated by the photovoltaic effect, is the current flowing into the diode, is the photovoltaic array capacitance, is the photovoltaic parallel resistance, is the photovoltaic series resistance, the photovoltaic array equation:
1 (1)
Formula: q is charge, K is Boltzmann constant, T is temperature. Since some of the parameters in (1) are difficult to determine, the mathematical model commonly
used in the project is:
173
Formulavoltage.
In the m
FormulaConside
formula (2)
Formula is the
of is 1.2
Formulapoint voltag
2.1.2. Phot
Based oray Simulin
2.2. MPPT
Photovo
a: is sho
maximum po
a: is theering the va) becomes:
a: is befoopen circui2 10 , the
a: is thege before th
tovoltaic ar
on the mathenk model ca
T controller
oltaic array
ort circuit cu
ower point a
e maximum ariation of th
fore the chait voltage bee value of β
e maximum he change.
rray Simul
ematical moan be establi
Figur
r algorithm
output P-V
urrent, a
vailable 、
power pointhe intensity
ange in lighefore the chis 5 10
power poin
link model
odel (2) ~ (5shed:
re 3 Photovo
m and Simu
curve as sh
and are
、 :
nt voltage, y S and the
ht intensity, hange, ΔT , and
nt current be
5) of the pho
oltaic array
ulink model
hown below
undetermine
is the maxtemperatur
1 ∆
changeis the PV a are the ch
efore the ch
otovoltaic ar
Simulink m
l
w:
ed coefficie
1
1 ln
ximum powe of the ph
1
es before thrray change
hanges of
1
1 ln
ange, i
rray, the foll
model.
1
ent, is o
n 1
wer point curhotovoltaic a
∆
he short-circe temperatur and :
n 1
is the maxim
lowing phot
(2)
open circuit
(3)
rrent. array T, the
∆1 (4)
cuit current,re, the value
(5)
mum power
tovoltaic ar-
)
t
)
e
)
, e
)
r
-
174
Figure 4 Photovoltaic array output P-V curve.
As can be seen in Figure 4, if you want the photovoltaic inverter in the photovoltaic power generation system to output the maximum power, the voltage needs to take the red dot position in the figure. Since the light intensity S and the photovoltaic array temperature T have a significant effect on the curve, in practice, S and T are in a state of constant change in general. Therefore, need to constantly track the maximum power point to ensure that the photovoltaic power generation system to maximize the output power.
2.2.1. MPPT controller algorithm
The maximum power MPPT controller research tracking algorithm commonly used constant voltage tracking method (Constant Voltage Tracking CVT (Perturbation), And Observation interference observation method referred to as P&O), the incremental conductance method (Incremental Con-ductance method referred to as INC), the incremental conductance method based on variable step size gradient. In this paper, the MPPT controller is designed based on the incremental conductivity method. The overall flow of the incremental conductivity algorithm is shown in the following figure:
Start
Read the initial voltage Ud
and the initial Current Id
Read the perturbed voltage Ud+1 and the perturbed current Id+1
Calculate the voltage change value ∆U and the current change value ∆I
∆U=0?
∆I=0? -∆I/∆U=I/U?
∆I>0? -∆I/∆U<I/U?
+∆U -∆U -∆U +∆U
End
NY
Y Y
NN
Y YN N
Figure 5 Incremental conductivity algorithm flow chart.
0 5 10 15 20 25 30 35 40 0
55
110
165
220
U/V P
/W
175
2.2.2. MPP
Based ocontroller S
2.3. Princi
Accordistrategy (Pstrategy) amaximum
2.3.1. PQ c
The maxon this valu
Based o
Formulapower calcwave,
Therefolowing figu
PT controll
on the overaSimulink m
iple and Sim
ing to the rPQ control and droop cpower, this
control stra
ximum powue, can outp
on KVL law
a (6) througculation formis zero, can
ore, the typiure:
Figure 7 P
ler Simulin
all flow chamodel can be
Figu
mulink Mo
research of strategy), ccontrol stras paper choo
ategy princ
wer anput the idea
w, the differe
gh the park mula, when
n be simplifi
ical block d
Pref
Qref
PQ control s
nk model
art of the ine established
ure 6 MPPT
odel of Phot
f domestic aconstant volategy (Droooses the PQ
ciple of PV
nd tracl active powential equat
transforman the AC sidied power c
diagram of P
2/3
-2/3
strategy of P
ncremental cd:
controller S
tovoltaic In
and foreignltage constaop control s
control stra
inverter
ced by MPPwer and reaction of photo
ation, can bde voltage fcalculation f
PQ control
id
iq
-+
+ -iqref
idref
/
/
ud
ud
PV inverter
conductivity
Simulink m
nverter Con
n scholars, ant frequencstrategy). Bategy as the
PT, the PV ictive powerovoltaic inv
be obtained for the standformula:
strategy for
u
+
+
PI
ωL
ωL
PI
r typical stru
y algorithm
model.
ntrol Strate
there are ccy control s
Based on Me PV inverte
inverter PQ r of AC sideverter is obt
in the rotatdard symme
r PV invert
udref
uqref
ud
+
-
+
ucture block
m, the follow
egy
constant powstrategy (V
MPPT for trer control st
control strae of PV invetained:
ting coordinetrical three
ter is shown
k diagram.
wing MPPT
wer controlV / f control
racking therategy.
ategy basederter.
(6)
nate systeme-phase sine
(7)
n in the fol-
T
l l e
d
)
m e
)
-
176
As showMPPT intoand sums wreference iinverter, anpower.
2.3.2. PV i
Based ostrategy of
3. Digita
3.1. DigitaElectric Po
China Esystem is high-perforpower simuoff the gridresults of results. Chsimulation
Figure
wn in figureo current refwith anis modulatend ultimatel
inverter PQ
on the typicf PV inverte
Fi
al analog hy
al analog hower Resea
Electric Powa real-tim
rmance digulator, enerd, dynamic the digital hina Electrmanageme
9 Distributi
e 7, the PVference valund ( =
ed by SPWMly change t
Q control st
cal structurer can be est
igure 8 PQ c
ybrid simu
hybrid simarch Institu
wer Researcme simulatio
ital simulatrgy storage reactive poanalog hyb
ric Power ent system in
ion network
inverter PQues an
=0) as the voM, control tthe active p
trategy Sim
e diagram tablished Si
control strat
lation of ph
ulation maute
ch Institute on of highion technolsimulator an
ower compebrid simulaResearch
nterface as
k digital ana
Q control stnd byoltage referthe duty rat
power outpu
mulink mod
of PQ contimulink mo
tegy Simuli
hotovoltaic
anagement
of distributh-speed anaogy and phynd RLC loa
ensation proation manag
Institute dshown belo
alog hybrid interface.
trategy convy equation (7rence valuestio of the put of photov
del
trol strategydel:
ink model o
c power gen
system of
tion networalog and Iysical equipad, it can simocess. It cangement sysdistribution ow:
2017-04
simulation
verts a7), is adjusts and ower electrvoltaic inve
y of PV inv
of PV invert
neration sys
distributio
rk hybrid si/ O inter
pment such mulate a varn be concludtem are conetwork a
-11
managemen
and mted by the P
, and ronic switcherter ideal a
verter, the
ter.
stem
on network
imulation mrface integras PV simuriety of equded that theonsistent wianalog dig
nt system op
measured byPI regulatorthe voltage
h of the PVand reactive
PQ control
k of China
managementration withulator, winduipment ande simulationith the real
gital mixed
peration
y r e
V e
l
a
t h d d n l d
177
3.2. Digita
The req120kVA andevice, 50k
Step 1: outlet, andload to star
Step 2: the main bvalue of vmeasuring transforme
Step 3: breaker sw
Step 4:software, s
Step 5measureme
Step 6: disconnectcopies the
4. SimulSystem
4.1. Photo
In the Mand draggeisolation trsimulation figure 10.
SimulatCPU clock
al analog hy
quired expernalog powekVA distribStart the a
d connect alrt the grid. Wiring acc
bus. The cuvoltage and
the voltager. Use the oOperate the
witch. operate th
set the light : observe ent feedbackThe oscillo
ts the circucorrespond
lation and
voltaic pow
Matlab / Simed into the ransformer m
Simulink
Figur
tion of the ked at 1.8GH
ybrid simu
rimental equer grid, 120kbution transfanalog powll the circu
cording to thurrent and vd the low ge at the looscilloscopee host comp
he host comintensity. the oscillok to the hos
oscope reachuit breaker, ding PNG.
Analysis o
wer generat
mulink connMatlab / S
model, and model. Pho
re 10 Photov
hardware eHz, 8GB me
lation meth
uipment is: kVA isolatiformer, circ
wer grid, theit breakers,
he line topovoltage are mvoltage sid
ower part oe to display puter control
mputer pho
oscope, PVst computer hes the specperforms a
of Grid - co
tion system
nected to FSimulink hasystem mootovoltaic g
voltaic grid
environmenemory.
hod for pho
10kW photion transforcuit breakere PV simul, contact ca
ology, the Pmeasured b
de current of the circu
the actual wl program to
otovoltaic p
V simulatorcontrol sof
cified time,a phased en
onnected P
m detailed m
Figure 3, Figas been int
odel, compogrid conne
d connected
nt for the in
otovoltaic p
tovoltaic pormer and tra, programmlator, close abinets and
PV throughby current cvalue of th
uit breaker waveform imo achieve st
power gene
r output aftware photo, stops recornlargement
Process in P
model appli
gure 6, Figutegrated RLsed of photcted simula
simulation
nstallation o
power gene
ower generaansformer n
mable RLC lthe networswitches, a
the PVS anclamp and vhe transformand the lowmage and wtart PVS inv
eration syste
and lower ovoltaic outrding, turnsof the rec
Photovolta
ication scen
ure 8 showLC model, covoltaic powation Simu
Simulink m
of MATLA
eration syst
ation simulaneutral pointload, 10Kwrk topologyand the pro
and circuit bvoltmeter. Tmer are mw voltage
waveform. verter, close
tem device
computer tput value. s off the PVcorded wave
aic Power G
nario
ws the Simulcircuit brea
ower generaulink model
model.
AB R2014a
tem
ation devicet groundingPVS.
y at the PVogrammable
breaker intoThe current
measured byside of the
e the circuit
simulation
equipment
V simulator,eforms and
Generation
link model,aker model,tion systeml shown in
PC, which
e, g
V e
o t y e
t
n
t
, d
n
, ,
m n
h
178
4.2. Photoresults
In this pas shown in
Figur
It can bobviously. photovoltathen quickl
4.3. Digita
Test tim100A. Oscvoltage A, phase valu
As showphotovolta
Figure 1
It can bvoltage anB-phase cuand with a
ovoltaic pow
paper, the cn Figure 11
re 11 Differ
be seen fromPV photov
aic grid instaly reduced t
al analog hy
me is 10 micilloscope dB, C phase
ue. wn in Figuraic grid insta
12 Photovol
be seen fromnd the grid urrent has avery small
wer genera
ircuit break1:
rent scale di
m the figurevoltaic outpantaneous pto 0A near,
ybrid simu
inutes, the display datae value, the
re 12, the oantaneous p
ltaic grid - c
m the figurecurrent. Ph
a significantamplitude o
-600
-400
-200
0
200
400
600
-200
-100
0
100
200
0 0.05-100
-50 0
50
100
ation system
ker closure t
istribution n
e that the Put current h
photovoltaicand gradua
lation resu
amplitude sa from top PV output c
oscilloscope photovoltaic
connected incurrent
e that there hotovoltaic t surge, thenof the shock
0.1 0.15
m detailed m
time point i
network mo
PV output vhas been inc output curally increase
ult analysis
set from topto bottom current A, B
e shows the c output vol
nstantaneouchanges wa
is no signifgrid-conne
n quickly cok.
0.2 0.25 0.3
model grid
is set to 0.4
odel convert
voltage and the vicinityrrent in the ed to stable.
of photovo
p to bottomin order to
B, C phase v
waveform tage and cu
us voltage anaveform.
ficant changected instanonverge nea
0.35 0.4
d - connecte
s position, P
ter output si
the grid cuy of 0A witgrid instant
oltaic grid c
m followed o express thvalue, and t
time: 28.75urrent chang
nd current a
ge in the insntaneous PVar the PV o
0.45 0.5
ed process
PV wavefor
ide active p
urrent are nth a very sm
ntly a signifi
connected p
by ± 500Vhe photovolthe dot curr
56s to 29.25ges in the gr
and grid - co
stantaneousV output Aoutput curre
simulation
rm changes
ower.
not changedmall shock,
ficant surge,
process
V, ± 10A, ±ltaic outputrent A, B, C
56s, for therid.
onnected
s PV outputA-phase and
nt 0A near,
n
s
d , ,
± t
C
e
t d ,
179
As shown in Fig. 13, the oscilloscope shows the waveform time: 251.001s to 291.001s, which is the PV output voltage current and the grid current change during the PV stabilization process.
Figure 13 Photovoltaic Grid - Connected Steady Process Voltage Current and Grid - Connected Current Variation Waveform.
It can be seen from the figure that the photovoltaic output voltage and the grid current are not changed obviously, and the PV output current has obvious change process. Affected by the inverter, three-phase current amplitude in a period of time to stabilize in a smaller value, after the A-phase current amplitude in the negative half-axis has a significant fluctuation after a slight increase and stability of about 10s, and then instantaneous increase and stability of about 20s, and then gradually increased 10s after the reduction to 10s before the amplitude, and finally gradually Increase and stabilize.
4.4. Comparison of simulation results
By comparing the results of the two simulations, we can see that Simulink simulation of the photovoltaic output current stability faster, but the process and digital analog hybrid simulation results are basically the same. In addition, the simulation results of grid connected PV system are consistent with the simulation results of the digital analog hybrid simulation. Therefore, the detailed model of the photovoltaic power generation system described in this paper can accurately realize the simulation of the real process of the photovoltaic power generation system.
5. Conclusion
In this paper, Simulink modeling is carried out for the detailed model of photovoltaic power generation system, and the process of grid connection of photovoltaic power generation system is simulated. Based on the distribution network digital analog hybrid simulation management system, the digital analog hybrid simulation of the grid - connected process of the photovoltaic power generation system was carried out. By comparing the waveforms of the two simulation results, the feasibility of the detailed model of the photovoltaic power generation system described in this paper is proved.
180
Acknowledgements
This work was supported by Project of Electric Power Research Institute of State Grid NingXia Electric Power Company (PDB11201601764) and Project of National High Technology Research and Development Program (863 Program) funded projects (2015AA050102)
References
[1] DING Ming, WANG Xiu-li, SONG Yun-ting, CHEN De-zhi, SUN Ming. A Review on the Effect of Large-scale PV Generation on Power Systems [J]. Proceedings of the CSEE, 2014, (01): 1-14.
[2] YANG Yong-heng, ZHOU Ke-liang. Photovoltaic Cell Modeling and MPPT Control Strategies [J]. TRANS-ACTIONS OF CHINA ELECTROTECHNICAL SOCIETY, 2011, (S1): 229-234.
[3] LI Shuai. Study on photovoltaic array MPPT control based on BP neural network [D]. Northeast Dianli Uni-versity, 2016.
[4] WANG Su-ying. A Maximum Power Point Tracking Technique for Partially Shaded Photovoltaic Systems and Control Method of Micro-Grid [D]. China University of Mining and Technology, 2014.
[5] WANG Su-ying, ZHANG Min. Research on Global Maximum Power Point Tracer of the Photovoltaic Array [J]. Electric Switchgear, 2015, (05): 59-62.
[6] YOU Guo-dong, LI Ji-sheng, HOU Yong et al. Modeling and MPPT control of partially shielded photovoltaic power generation system [J]. Power System Technology, 2013, 11: 3037-3045.
[7] WANG Cheng-shan, LI Yan, PENG Ke, et al. Over-view of Typical Control Methods for Grid-Connected Inverters of Distributed Generation [J]. Proceedings of the CSU-EPSA, 2012, (02): 12-20.
[8] WU Li-bo. Research and Implementation of Control Strategy in Grid-connected Photovoltaic Systems [D]. Tsinghua University, 2006.
[9] WU Yun-ya, KAN Jia-rong, XIE Shao-jun. Control Strategy Design for Inversters in Low Voltage Microgrids [J]. Automation of Electric Power Systems, 2012, (06): 39-44.
[10] LIU Fei. Research on Operation Control of Three-Phase Grid Connected Photovoltaic Power System [D]. Huazhong University of Science and Technology, 2008.
181